Overclock.net › Forums › Overclock.net Forum › FAQs › Does my PSU Always Use the MAX Rated Wattage?
New Posts  All Forums:Forum Nav:

Does my PSU Always Use the MAX Rated Wattage?

post #1 of 10
Thread Starter 
A very common misconception indeed is the idea that computer Power Supply Units (PSU's) always use their MAX rated wattage. Such an idea is absurd. If it were true, you would simply be "burning" watts into thin air. Computer's and their components draw in only the amount of power they need at one moment in time. If this power need were to go up, then the PSU would simply take in more AC power, convert it, and give your components the power they need!
In this FAQ, I will demonstrate a test to tell how many Watts my computer uses while Idle and while Under stress. I will be measuring the total watts used by my Computer with my UPS backup battery. The software included with this piece of hardware comes with a moniter that shows the percentage of power being used at any given time. The UPS I will be using is rated at 660 Watts. Thus, the power usage percent meter would show 100% if 660 watts were being used, 50% if 330 were being used, etc. The computer I will be testing has a 180 Watt PSU, so the meter will never go beyond about 27 percent...and that would not be done unless every piece of equipment was going full blast inside the computer.

My Test Computer Specs:

DELL Dimension 4500S
P4 @ 1.80 GHz
768 MB PC-2700 RAM
Integrated Video Accelerater
40GB 7200RPM Hard Drive
Stock Heatsink/Fan Assembly
CD-RW Drive (Which will not be used)
Floppy Drive (Which will not be used)

This is not the ideal setup that I'd like to use to show this test, but right now, it is all I have...bear with me here. If you don't have integrated Video, then you would see an even bigger change from Idle to Load.

For the test procedure, I restarted the computer. I opened windows task manager, CPU-Z (To show you my specs...) and the Belkin UPS Moniter and let the computer sit for about 10 minutes to get its processes over with...(virus update..all that stuff.) After the wait, I took a screen shot to show the power consumption meter. The meter read 6% at IDLE. This means that my computer, while sitting IDLE uses about 40 Watts - a small light bulb. Here is the IDLE setup picture:




Now, on to the LOAD setup. For this setup, I restarted my computer once more, allowed it to sit and finish its processes, then opened a few programs. I opened the UPS moniter and the Windows Task Manager, along with Folding @ Home which was configured to use 100% processor and also ATI Tools to load the integrated graphics. I started everything up and let it go for 5 minutes. I then took a screen shot and came up with this:




17% loading level. That is a fairly big leap for a small computer like this. We see that the processor draws alot of power when being used under stress. We then take the equation of 660 Watts (the max UPS wattage) x .17 (17%) = 112.2 Watts. Nowhere near the max rated PSU wattage of 180, but we weren't using the HD or CD drive much, so...

In conclusion to this testing, we now see that a PSU does NOT use its max wattage when Idle. So next time you want to leave your computer on all night, just think...as long as you aren't running SuperPI along with Folding @ Home among other stressers, you won't be using up all of that electricity!
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
post #2 of 10
Nice, I always thought I was wasting energy...I thought my power supply always used 350 watts.
post #3 of 10
Thread Starter 
Nope, your computer components draw what current they use, however, some power is wasted and goes into the air as heat. Depending on how much power you are demanding from the psu, the more loss you will get, but thats a totally different FAQ...
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
post #4 of 10
where can i download Belkin UPS Moniter
    
CPUGraphicsOS
Intel Core i7 Nvidia GeForce GTX 460m Win7 64bits 
  hide details  
Reply
    
CPUGraphicsOS
Intel Core i7 Nvidia GeForce GTX 460m Win7 64bits 
  hide details  
Reply
post #5 of 10
I wanna monitor the UPS too... there watching me...
Craiginator
(13 items)
 
  
CPUMotherboardGraphicsRAM
e6420 - L712a517 Abit AB9 Pro P965 XFX 7800 GTX 2GB GEIL PC2-8500 Ultra 
Hard DriveOptical DriveOSMonitor
2x Wd 160gb Raid 0 Asus Dvd/Cd-RW Ubuntu / XPlite 22' Acer ws X222W 
KeyboardPowerCaseMouse
G15 Antec 550 True Power Antec 900 G5 
Mouse Pad
Yes Please. 
  hide details  
Reply
Craiginator
(13 items)
 
  
CPUMotherboardGraphicsRAM
e6420 - L712a517 Abit AB9 Pro P965 XFX 7800 GTX 2GB GEIL PC2-8500 Ultra 
Hard DriveOptical DriveOSMonitor
2x Wd 160gb Raid 0 Asus Dvd/Cd-RW Ubuntu / XPlite 22' Acer ws X222W 
KeyboardPowerCaseMouse
G15 Antec 550 True Power Antec 900 G5 
Mouse Pad
Yes Please. 
  hide details  
Reply
post #6 of 10
Thread Starter 
Quote:
Originally Posted by hermit
where can i download Belkin UPS Moniter
Well you have to have a UPS backup battery. I was just using that analogy to show that your psu doesn't always use the maximum rated wattage.
www.belkin.com
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
post #7 of 10
do i 'need' a 470w psu to run my stuff??
    
CPUGraphicsOS
Intel Core i7 Nvidia GeForce GTX 460m Win7 64bits 
  hide details  
Reply
    
CPUGraphicsOS
Intel Core i7 Nvidia GeForce GTX 460m Win7 64bits 
  hide details  
Reply
post #8 of 10
Thread Starter 
With all the hardware, I'd say you probably do...7800GTX pulls alot of power and along with that processor and 2 HD's, I'd say you are probably pulling 375-450 watts and then you have to think in terms of wattage loss to heat.
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
post #9 of 10
so, my PSU is fine for what i have
    
CPUGraphicsOS
Intel Core i7 Nvidia GeForce GTX 460m Win7 64bits 
  hide details  
Reply
    
CPUGraphicsOS
Intel Core i7 Nvidia GeForce GTX 460m Win7 64bits 
  hide details  
Reply
post #10 of 10
Thread Starter 
Quote:
Originally Posted by hermit
so, my PSU is fine for what i have
It should be...you might want to open a thread in the power supply section and get everyone's opinion or facts
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
The Crushanator
(13 items)
 
  
CPUMotherboardGraphicsRAM
Intel E6400 @ 3.36GHz DFI Blood Iron P35-T2RL Nvidia 260GTX 2x1GB Crucial Ballistix PC2-6400 
Hard DriveOSMonitorKeyboard
RAID 0 Seagate 7200.10 Windows XP Pro w/SP3 ViewSonic G220fb CRT A board with keys 
PowerCaseMouse
Sunbeamtech NUUO 550Watt Thermaltake Kandalf Tower Logitech Mx 518 
  hide details  
Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: FAQs
Overclock.net › Forums › Overclock.net Forum › FAQs › Does my PSU Always Use the MAX Rated Wattage?